I am a bit confused on EPSG:4326 and EPSG:900913. I thought that they were both same. Though as I am placing my features over GMaps, which is EPSG:4326, I need to define the srsname of the WFS layer as EPSG:900913 to get it into the right place. If I define srsname as 4326 it is projected somewhere completely wrong.

Could someone explain it a bit more in detail as to what is wrong here?

As a point of trivia: 900913 was originally rejected as a credible projection by European Petroleum Survey Group (EPSG) so Google (who invented it for the web) gave it their own number, which if you type it on an old fashioned calculator spells 'googlE' (substitute '9' for 'g' and squint a bit). Eventually EPSG relented and allowed 900913 into its geodetic repository but gave it the number 3857.
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MappaGnosisJan 24 '13 at 8:10

1

@arcsump, 900913 (3857) does not use an authalic sphere. It uses a sphere with a radius equal to the semimajor axis of WGS 1984 ellipsoid.
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mkennedyJan 24 '13 at 17:52

2 Answers
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They are not the same. EPSG:4326 refers to WGS 84 whereas EPSG:900913 refers to WGS84 Web Mercator. EPSG:4326 treats the earth as an ellipsoid while EPSG:900913 treats it as a sphere. This affects calculations done based on treating the map as a flat plane which is why your features got plotted on the wrong places.